Datenblatt-Suchmaschine für elektronische Bauteile |
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AD5222BR100 Datenblatt(PDF) 9 Page - Analog Devices |
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AD5222BR100 Datenblatt(HTML) 9 Page - Analog Devices |
9 / 10 page AD5222 –9– REV. 0 PROGRAMMING THE VARIABLE RESISTOR Rheostat Operation The nominal resistance of the RDAC between Terminals A and B are available with values of 10 k Ω, 50 kΩ, 100 kΩ, and 1 MΩ The final three characters of the part number determine the nominal resistance value, e.g., 10 k Ω = 10; 50 kΩ = 50; 100 kΩ = 100; 1 M Ω = 1M. The nominal resistance (R AB) of the VR has 128 contact points accessed by the wiper terminal, plus the B terminal contact. At power ON, the resistance from the wiper to either end Terminal A or B is approximately equal. Pulsing the CLK pin will increase the resistance from the wiper W to Terminal B by one unit of RS resistance, see Figure 33. The resistance RWB is determined by the number of pulses applied to the clock pin. Each segment of the internal resistor string has a nominal resistance value of RS = RAB/128, which becomes 78 Ω in the case of the 10 k Ω AD5222BR10 product. Care should be taken to limit the current flow between W and B in the direct contact state (RWB code = 0) to a maximum value of 20 mA to avoid degradation or possible destruction of the internal switch contact. Like the mechanical potentiometer the RDAC replaces, it is totally symmetrical (see Figure 3). The resistance between the wiper W and Terminal A also produces a digitally controlled resistance RWA. When these terminals are used the B-terminal should be tied to the wiper. The typical part-to-part distribution of RBA is process-lot- dependent having a ± 30% variation. The change in R BA with temperature has a –35 ppm/ °C temperature coefficient. The RBA temperature coefficient increases as the wiper is pro- grammed near the B-terminal due to the larger percentage contribution of the wiper contact switch resistance, which has a 0.5%/ °C temperature coefficient. Figures 9 and 10 show the effect of the wiper contact resistance as a function of code setting. PROGRAMMING THE POTENTIOMETER DIVIDER Voltage Output Operation The digital potentiometer easily generates an output voltage proportional to the input voltage applied to a given terminal. For example connecting A-terminal to 5 V and B-terminal to ground produces an output voltage at the wiper which can be any value starting at zero volts up to 1 LSB less than 5 V. Each LSB of voltage is equal to the voltage applied across Terminals AB divided by the 128-position resolution of the potentiometer divider. The general equation defining the output voltage with respect to ground for any given input voltage applied to Termi- nals AB is: VW(D) = D/128 × V AB + VB (1) D represents the current contents of the internal up/down counter. Operation of the digital potentiometer in the divider mode results in more accurate operation over temperature. Here the output voltage is dependent on the ratio of the internal resistors not the absolute value, therefore, the drift improves to 20 ppm/ °C. |
Ähnliche Teilenummer - AD5222BR100 |
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Ähnliche Beschreibung - AD5222BR100 |
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